Engine lubrication systems provide many functions such as wear protection, corrosion protection, and engine cooling. One drawback is that engine power is diverted to operating a high pressure oil pump to distribute oil through passages in the engine, which weighs against engine efficiency. Overhead cam engines present a challenge to adequately and reliably lubricate the valve train without creating an undue demand on the engine lubrication system.
In an OHC engine, excess oil may flow out of a camshaft journal bearing and return to an oil reservoir without lubricating other valve train components. This unpressurized oil presents an opportunity for providing lubrication to other valve train components.